Specify -mtriple=x86_64 in an X86-specific dwarf test

On the PPC bot, the %llc_dwarf substitution does not contain an -mtriple
argument. This can cause the wrong backend to be exercised.

This causes issues because the backends differ in when they decide to
emit tail calls:

  http://lab.llvm.org:8011/builders/clang-ppc64be-linux-multistage/builds/12440

This is mostly a speculative fix as I don't have a PPC machine to test
with.

llvm-svn: 343893

Author: vedantk

llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs.ll

@@ -13,8 +13,8 @@
 ; UNSUPPORTED: cygwin,windows-gnu,windows-msvc
 
 ; REQUIRES: object-emission
-; RUN: %llc_dwarf < %s -o - | FileCheck %s -check-prefix=ASM
-; RUN: %llc_dwarf < %s -filetype=obj -o %t.o
+; RUN: %llc_dwarf -mtriple=x86_64-- < %s -o - | FileCheck %s -check-prefix=ASM
+; RUN: %llc_dwarf -mtriple=x86_64-- < %s -filetype=obj -o %t.o
 ; RUN: llvm-dwarfdump %t.o -o - | FileCheck %s -check-prefix=OBJ -implicit-check-not=DW_TAG_call_site
 ; RUN: llvm-dwarfdump -verify %t.o 2>&1 | FileCheck %s -check-prefix=VERIFY
 ; RUN: llvm-dwarfdump -statistics %t.o | FileCheck %s -check-prefix=STATS